Blower nozzle

ABSTRACT

A blower nozzle, especially for heating or cooling web-like materials, especially plastic foil webs, comprises at least one distribution chamber (11) and often a supply chamber (7). In the improvement, between the supply chamber (7) and the distribution chamber (11) there is at least one other chamber (9), so that the treatment gas can flow from the supply chamber (7) to the at least one further chamber (9) via an overflow aperture arrangement (17) and from the further chamber (9) via another overflow aperture arrangement (23) into the distribution chamber (11) for further conveyance to the outlet aperture arrangement (27).

This application is the U.S. National phase of International ApplicationPCT/EP97/02921 which designated the U.S.

BACKGROUND OF THE INVENTION

The invention relates to a blower nozzle for heating and coolingweb-like materials.

Blower nozzles of this type are used, for example, for heating orcooling web-like materials, in particular in the production of plasticfoil. In this case, the blower nozzle is arranged transversely, i.e.generally perpendicularly, to the take-off direction of the materialweb, and thus transversely to the web running direction, above and/orbelow the material web.

It is particularly important for the foil process that the outflow fromthe nozzles is even, since uneven heating of the plastic foil duringprocessing can have negative effects on the thickness profile. This isbecause slightly warmer regions are stretched more and are thus thinnerthan relatively colder plastic foil regions, which then obtain asomewhat thicker foil cross section. Uneven heating or cooling of thefoil also leads, however, to a deterioration in the flatness of thefinal product.

Even blowing is particularly crucial for the production of ultrathinfilms or foil whose thickness can be reduced down to about 0.4 μm.

Various proposals have already been made to even out the outflow speedfor heating or cooling continuous webs of material, in particularplastic foil webs. EP-A1-0 377 311 proposes a blower nozzle having twosupply chambers which are seated next to one another, extendtransversely to the take-off direction of the material web, areprovided, in each case opposite one another, with a supply aperture forthe hot gas of the hot air, and are closed at their respective, oppositeend. The cross section of the respective supply chamber decreases in aweb-shaped manner from the supply aperture to the opposite, closed endparallel, in the side view, to the take-off direction of the plasticfoil web. A distribution chamber is then seated below the two supplychambers arranged next to one another, with the result that the oppositehot gas flowing in at the end side via the supply chambers can then passvia overflow apertures, arranged between the two supply chambers and thedistribution chamber, essentially transversely to the plane of thematerial web into the distribution chamber and from there can emerge ina transverse direction transversely to the plastic foil web via outletapertures situated at the bottom.

Since two supply chambers which are symmetrically opposite to thecentral longitudinal direction of the plastic foil web are thusprovided, it is possible for an equal distribution of pressure to beobtained which, even if it is not even is nevertheless at leastsymmetrical with respect to the cross section of the plastic foil web(i.e. transversely to the take-off direction thereof), thus enabling theplastic foil web to be subjected to the blowing action of air or gas asevenly as possible over the entire width of the blower nozzle.

However, this requires an increased outlay since two supply ducts areprovided, which have to be supplied with hot gas or cooling gas(generally air) in each case on opposite sides, i.e. on both sides ofthe material web being advanced, in each case via a separate supplyaperture. However, this results in relatively poor accessibility to theblower nozzle in particular if it is installed in an oven.

An essentially two-part veneer web drier has been disclosed, forexample, in DE 30 35 417 A1. The nozzle box includes a perforated platewhich runs obliquely from bottom to top, is provided with holes anddivides the nozzle box into a pressure space and a suction space, thesuction space being connected to the intake side and the pressure spacebeing connected via the delivery side to circulating fans. Even a veneerweb drier of this type does not result in the desired, completely evendistribution and/or even gas outlet speed of the supplied hot gas flowover the entire length of the nozzle box.

In the case of the blowing device which is disclosed in DE 37 04 910 C1or DE 36 26 171 C1 and is intended for blowing a treatment medium onto amaterial web moving in the longitudinal direction, just one chamber isprovided which is simultaneously used as the supply and distributionchamber. In order to be able to supply hot gas at the two opposite, endsupply apertures from just one side of the material web, some of the hotgas is supplied via a separate supply duct to the opposite, endconnection aperture of the distribution chamber, via the additionalsupply duct, and is conducted into the distribution chamber.

A corresponding principle for a nozzle box for a device for the heattreatment of webs of endless fabric, in particular textile webs, hasbeen disclosed to this extent in DD 253 666 A1 too.

Suspension nozzles have been disclosed, for example, in US patents U.S.Pat. Nos. 5,156,312 and 5,395,029. The medium can emerge from a supplychamber via two lateral control chambers upward in the direction of thematerial web which is being guided past and is to be treated, it beingpossible for the individual, lateral control chambers to be opened orclosed in such a manner that an air flow in the direction of thetake-off direction of the material web to be treated, a flow directionin the opposite direction thereto, or a symmetrical flow direction canbe produced to the extent that some of the gas flowing out is deflectedin the take-off direction of the material web and in the oppositedirection.

Finally, DE 38 15 211 C2 has disclosed the design of a suspension nozzlehaving a plurality of chambers, which nozzle, however, because of itsdesign results in the web of endless fabric W coming to lie between theoutlet nozzles in a cross-sectionally rippled manner. A suspensionnozzle of this type in particular cannot be used in the production ofplastic foil webs which is advanced via tenter hooks acting laterally onthe plastic foil web and is optionally stretched in the longitudinaland/or transverse direction.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide acomparatively simply designed blower nozzle for treating, in particularheating and/or cooling continuous webs of material, which blower nozzlemakes possible uniform distribution and/or an even outlet speed of thesupplied treatment medium (generally hot or cool air flow) over theentire length of the nozzle box, i.e. over the entire width of thematerial web being advanced.

In an amazingly simple manner, the present invention provides a blowernozzle which ensures a clearly improved, uniform distribution and evengas outlet speed from the nozzle box into the surrounding operationalspace.

To this end, the invention provides at least a three chamber systemwhich comprises, on the one hand, a supply chamber for supplying thetreatment gas (heating or cooling gas), a distribution chamber fromwhich the gas ultimately emerges in the direction of the material webbeing advanced, by means of a component directed transversely to saidweb, and a further chamber arranged between the supply and thedistribution chamber, preferably in the form of a pressure compensationchamber.

The at least one further chamber serves to compensate for the pressureof the gas supplied via the supply chamber. In the distribution chamberthe dynamic pressure of the gas or air flow can then ultimately bechanged into stagnation pressure resulting in further evening out of thepressure, thereby enabling even distribution of the gas flow to theoutlet apertures.

In a particularly preferred embodiment of the invention provision ismade for the overflow apertures in each case to be arranged from onechamber to the next chamber in such a manner that the plane of theaperture directions and hence the flow directions of the gas throughthese apertures are aligned, with respect to the overflow apertures atthe transition to the next chamber or to the alignment of the outletapertures--via which the treatment gas emerges in the direction of thematerial web--in each case transversely to one another, i.e. are alignedpreferably perpendicularly or essentially perpendicularly to oneanother. As a result, the gas flow is in each case deflected in thetransition from the supply chamber to the pressure compensation chamber,from the pressure compensation chamber to the distribution chamber andfrom the distribution chamber via the outlet apertures in the directionof the material web to be treated, as a result of which a high-gradeeven gas outlet speed from the nozzle box and a high-grade evendistribution of the supplied hot gas flow over the entire width of thematerial web being advanced can be achieved.

Altogether, in particular when realizing preferred embodiments, thefollowing advantages can thus be achieved:

An even distribution of the supplied gas flow over the entire width ofthe material web to be treated or the entire blower nozzle.

An even gas outlet speed from the nozzle box into the surroundingoperational space.

A constant quality of distribution from the blower nozzle or the nozzlebox with regard to the gas outlet speed at different volumetric flows,with deviations better than

±4% at V_(max)

±10% at V_(min)

where ##EQU1## A more even heat transmission coefficient between nozzlebox and operative surface outside the nozzle box (for the outletapertures to the material web it being possible for the parameters ofaperture size, aperture pitch and distance between the material web andthe outlet apertures of the air nozzle to be matched optimally to oneanother).

A low pressure loss between a fan connected upstream of the blowernozzle and the outlet apertures of the blower nozzle (of the nozzlebox); further improvements can still then be achieved, the area ratiosof the duct cross sections and chamber cross sections are matched to oneanother and if the chamber geometries are also designed in a customarymanner such that they are a favorable in terms of flow.

A high-grade insensitivity of the blower nozzle to changed operatingtemperatures.

Ensuring that the treatment medium impacts on the material web to betreated in an as perpendicular a manner as possible.

The nozzle geometry can be used for nozzle boxes of differing length,even for ovens, i.e. in particular for oven constructions having adiffering working width. It is not necessary to change the nozzle designin the case of a differing oven width or differing width of the materialweb.

Low Production costs for the blower nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a schematic perspective representation of a blower nozzleembodying the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is explained in more detail below with reference to anexemplary embodiment.

The drawing shows, in a schematic, perspective representation, a blowernozzle having a nozzle box 1 which extends in its longitudinal directiontransversely to the take-up direction 3 of a material web 5. In theexemplary embodiment shown, the material web 5 comprises a plastic filmwhich is subjected to longitudinal and/or transverse stretching, forexample, in a stretching installation. In the perspective representationaccording to the attached figure, only some sections of the nozzle box 1are shown. The material web is provided with broken-through areas inorder better to show the nozzle box below the material web. The actualfoil widths can clearly be wider than the dimensional informationaccording to the attached drawing leads one to assume.

A gaseous treatment medium, generally air, for example for heating orcooling the foil, can be supplied in the nozzle box. In this respect,some mention is also made below of hot or cooling gas.

In the exemplary embodiment shown, the nozzle box 1 has a rectangularcross section transversely to its longitudinal extent. In principle, itcomprises a multichamber system, in the exemplary embodiment shown, afirst chamber 7, a second chamber 9 and a third chamber 11, which arealso called supply chamber 7, pressure compensation chamber 9 anddistribution chamber 11, respectively, below.

The nozzle box 1 has a supply aperture 13, which provides a connectionto the supply chamber 7, only on its one end side represented in thedrawing. In other words, the end side which can be seen in the drawing,i.e. the end walls of the pressure compensation chamber 2 and of thedistributer chamber 3, is closed by an end wall 15.

The opposite, further end wall (not illustrated in more detail in thedrawing) on the other wide side of the material web 5 is closed, withthe result that the gas or treatment medium is supplied only on oneside, via an end supply aperture 13, which has advantages in terms ofconstructional engineering.

In the longitudinal direction of the nozzle box 1, and hence intransversely to the take-up direction 3, i.e. generally perpendicularlyto the take-off direction 3, there is provided at least one overflowaperture arrangement 17 which, in the exemplary embodiment shown,consists of a multiplicity of overflow apertures 17' provided along aline arranged transversely to the take-off direction 3.

Via this overflow aperture arrangement 17, the supplied gas can flowfrom the supply chamber 7 over the entire length of the supply chamberinto the pressure compensation chamber 9.

In each case at least one overflow aperture arrangement 23 having (inthe exemplary embodiment shown) a multiplicity of overflow apertures23', which are arranged one behind another and hence transversely to thetake-off direction 3, are likewise provided opposite one another on twoopposite pressure-compensation chamber walls 21, via which apertures 23'the gas can flow over from the pressure compensation chamber 9 into thedistribution chamber 11.

Finally, via an outlet aperture arrangement 27, the gas can emerge inthe direction of the material web 5 by means of a transverse component,i.e. essentially using a component directed perpendicularly to thematerial web 5. The outlet aperture arrangements 27 are provided in abox wall 29 on the material-web side and, in the exemplary embodimentshown, comprise a multiplicity of outlet apertures 27' arranged in amanner such that they are offset from one another in the longitudinaland transverse direction on the box wall 29.

Finally, in the exemplary embodiment shown, the supply chamber 7 isarranged in the central region of the nozzle box 1, the distributionchamber 3 adjoining the supply chamber 7 in a spatial arrangement onthat side which is remote from the material web 5.

In the exemplary embodiment shown, the distribution chamber 11encompasses the centrally arranged supply chamber 7 and, at leastpartially, in that region which faces away from the material web 5, alsothe pressure compensation chamber 9.

It is furthermore shown in the exemplary embodiment that thedistribution chamber 11 can basically be split or divided into two, i.e.by means of a partition 30 which lies in the longitudinal direction ofthe nozzle box 1, preferably in a vertical central longitudinal planeperpendicularly to the material web 5. Compensation apertures 31 are,however, furthermore also provided in this partition so that pressurecompensation in the two parts 11a and 11b of the distribution chamber 11takes place if necessary.

The arrangement in this case is such that, for example hot or coolinggas--generally hot or cooling air--coming from a fan is supplied to thesupply aperture 13 and hence to the supply chamber 7. Since the threechambers of the blower nozzle extends virtually over the entire lengthof the blower nozzle, i.e. over the entire width of the material web tobe treated, the treatment gas overflows over the entire length of thesupply chamber, i.e. over the entire longitudinal extent of the overflowaperture arrangement 17, from the supply chamber 1 into the pressurecompensation chamber 9. The gas flow is thus deflected via this overflowaperture arrangement 17 and uniformly metered over the entire length ofthe nozzle box. In this arrangement, the flow direction 37 through theoverflow aperture arrangement 17 is transverse, i.e. perpendicular oressentially perpendicular (i.e. at an angle of 90°±≦45°, in particular90°±≦30° or 90°±≦15° to the flow direction 35 in the supply chamber 7,the flow direction 35 running in the longitudinal direction and hencetransversely (perpendicularly) to the take-off direction 3 of thematerial web 5.

In the pressure compensation chamber 9 pressure compensation over theentire length of the nozzle box is then possible.

The gas can then overflow via the subsequent overflow aperturearrangement 23 into the distribution chamber 11, the dynamic pressure ofthe gas flow being converted into stagnation pressure. This achieves afurther evening out of the pressure and an even distribution of the gasflow to the outlet apertures 27'.

The overflow aperture arrangement 23 is likewise again arranged in sucha manner that the flow direction 39 through this second overflowaperture arrangement 23 again transverse, i.e. essentially perpendicularto the first flow direction 35, as the gas flow overflows from thesupply chamber 7 to the pressure compensation chamber 9, but alsoessentially comes to lie transversely to the flow direction 37. Theangle of the flow direction 39 is intended likewise again to amount toapproximately 90°±≦45°, in particular 90°±≦30° or 90°±≦15° to the flowdirection 35 and/or 37.

Via the outlet apertures 27 the stagnation pressure in the distributionchamber 11 is then converted into dynamic pressure in the outflowapertures 27' of the distribution chamber.

The outlet flow direction 41 through the outlet apertures 27' is againlikewise essentially perpendicular to the preceding flow directions 35,37 and/or 39. In this case too the angle deviations to the perpendicularcan amount to 90°±≦45°, in particular 90°±≦0° or 90°±≦15°.

The quality of distribution of the nozzle box or of the gas outlet speedin the event of differing volumetric flows can also be further improvedif the individually mentioned overflow aperture arrangements 17, 23 andthe outlet apertures 27' consist of holes, in particular round holes,which may, for example, be punched. This enables not only lowmanufacturing tolerances to be achieved but also the pitch of the holecan be very precisely configured.

A particularly low pressure loss in the blower nozzle between the fanand outlet aperture of the nozzle box can be achieved by the area ratiosof the duct cross sections and of the chamber cross sections beingmatched to one another. As a result, the chamber geometries can also bedesigned in a manner which is favorable in terms of flow.

Above all, the nozzle box mentioned is extremely insensitive to changedoperating temperatures.

From the cross-sectional representation of the nozzle box 1 it can alsobe seen that the external housing comprises a cross-sectionallyrectangular nozzle box. The supply chamber 7 and the pressurecompensation chamber 9 have a common housing wall which consists, forexample, of a plate and surrounds the two opposite sides 21. The platemay be one which is appropriately edged and in cross section is designedin the manner of an inverted U. The two side walls 21 are thus connectedvia an upper connecting section 43 which is, however, located within thenozzle box 1. Only the lower ends of the side walls 21 are attachedinternally, in an airtight manner, to the side walls of the nozzle box1.

Only one intermediate plate 45, in which the overflow apertures 17' arearranged, is used as a separating plate between the supply duct 7 andthe connecting duct 9, this separating plate 45 likewise being fastenedinternally, by means of corresponding flange sections, in an airtightmanner, to the opposite side walls 21.

To achieve sufficient stability use is then finally made of theabovementioned partition 30 which extends between the upper connectingsection 43 of the supply duct and the inside of the box wall 29 on thematerial-web side and is fastened to the connecting section 43 and thebox wall 29 via corresponding flange sections which in the exemplaryembodiment shown protrude in the opposite direction.

Deviating from the exemplary embodiment shown, the spatial sequence ofthe chambers could also differ to the extent that the supply chamber 7is situated the greatest distance away from the outlet apertures 27',and is adjoined, in the direction of the material web 5, by the pressurecompensation chamber 9 and then the distribution chamber 11.

Finally, use can also be made of a chamber system which comprises morethan a total of three chambers, in which rather than only one pressurecompensation chamber, for example, two or more pressure compensationchambers 9 connected one after the other and having correspondingoverflow aperture arrangements between the pressure compensationchambers are provided.

What is claimed is:
 1. A blower nozzle for heating or cooling a materialweb, comprising:an elongated nozzle housing having a longitudinal axisextending in operation in a direction transverse to a feed direction ofthe material web, said nozzle having an outer wall and a plurality ofchamber walls provided within said outer wall to define a plurality ofchambers for determining a flow path of a treatment gas through saidhousing, said chambers including a first, supply chamber for receivingtreatment gas and for supplying said treatment gas to a remainder ofsaid chambers, at least one second chamber for receiving treatment gasfrom said supply chamber via a first aperture arrangement providedbetween the supply chamber and said at least one second chamber, and athird, distribution chamber for receiving treatment gas flowing fromsaid at least one second chamber via a second aperture arrangement,wherein said third, distribution chamber extends in a directiontransverse to the feed direction of the material web and wherein a thirdaperture arrangement is defined through an outlet portion of said outerwall and in communication with said distribution chamber so that flowtherethrough is in a direction generally transverse to the feeddirection of the material web, said third aperture arrangement beingdefined to extend over substantially an entire width of the materialweb.
 2. A blower nozzle according to claim 1, wherein each of said firstand said second aperture arrangements extend over at least one ofsubstantially the entire width of the material web and essentially overan entire length of the nozzle housing.
 3. A blower nozzle according toclaim 1, wherein each of said first and said second aperturearrangements comprises at least one slotted recess.
 4. A blower nozzleaccording to claim 1, wherein each of said first and said secondaperture arrangements comprise a plurality of round holes.
 5. A blowernozzle according to claim 4, wherein each said plurality of round holesis oriented in at least one line extending in the longitudinal directionof the nozzle housing and such that the lines are laterally offset fromone another.
 6. A blower nozzle according to claim 1, wherein the nozzlehousing has first and second longitudinal ends and further comprising asupply aperture for supplying treatment gas to said first, supplychamber via solely one of said two longitudinal ends.
 7. A blower nozzleaccording to claim 1, wherein a flow direction of treatment gas fromsaid first, supply chamber into said at least one second chamber isgenerally transverse to a flow direction along which treatment gas flowsin said first, supply chamber.
 8. A blower nozzle according to claim 1,wherein a treatment gas flow direction from said at least one secondchamber to said third, distribution chamber is generally transverse to aflow direction along which the treatment gas flows in the first, supplychamber.
 9. A blower nozzle according to claim 1, wherein said thirdaperture arrangement is oriented so that the flow direction out of thethird, distribution chamber is generally transverse to the flowdirection from said at least one second chamber into said third,distribution chamber.
 10. A blower nozzle according to claim 7, whereinthe directions of flow from said first, supply chamber to said secondchamber, from said second chamber to said third chamber, and out fromsaid third chamber are each disposed generally transverse to one anotherso that the respective flow directions are inclined to one another by anangle of between about 45° and 135°.
 11. A blower nozzle according toclaim 1, further comprising a partition wall dividing said third,distribution chamber into a first distribution chamber part and a seconddistribution chamber part, each said chamber part extending in a widthwise direction generally perpendicularly to said outlet portion of saidouter wall in which said third aperture arrangement is defined.
 12. Ablower nozzle according to claim 11, wherein a plurality of compensationapertures are defined through said partition wall.
 13. A blower nozzleaccording to claim 1, wherein the distribution chamber overlaps at leasta portion of at least one of said first, supply chamber and said secondchamber.
 14. A blower nozzle according to claim 1, wherein said secondaperture arrangement is provided in each of first and second chamberwalls defined between said at least one second chamber and said third,distribution chamber, said first and second chamber walls being offsetin the feed direction of the material web and each extend in a directiongenerally transverse to the material web.
 15. A blower nozzle accordingto claim 1, wherein said at least one second chamber is disposed on adiametrically opposite side of said first, supply chamber with respectto said outlet portion of said outer wall.
 16. A blower nozzle accordingto claim 1, wherein said at least one second chamber is disposed on aside of said first, supply chamber that faces the third aperturearrangement.
 17. A blower nozzle according to claim 1, wherein saidplurality of chamber walls include first and second chamber wallsdefining side walls of the first, supply chamber and of the at least onesecond chamber, said first and second chamber walls diverging away fromone another in a direction away from said outlet portion of said outerwall.
 18. A blower nozzle according to claim 1, wherein said at leastone second chamber comprises a pressure compensation chamber forreceiving treatment gas from said supply chamber and directing saidtreatment gas to said distribution chamber.